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- Author or Editor: Temel Oguz x
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Abstract
Along the southern Turkish continental shelf, the intensity of the observed mean flow has a considerable degree of variability. The relatively strong currents along the straight portion of the coast is reduced significantly in the nearshore region upon encountering irregularities in the form of bays and headlands. As a possible explanation of such blockage by coastal irregularities, a linear, homogeneous wind-stress free model is presented incorporating the constraints of topographic steering and linear bottom friction. Solutions are given for an idealized case of an abrupt indentation on a straight coast adjoining a linearly deepening shelf. The directions preference of blocking and the applicability of boundary layer approximations am discussed. Numerical solutions are obtained for the realistic bathymetry and coastal configuration along the southern Turkish continental shelf. The concepts developed are applied to the observed blocking features.
Abstract
Along the southern Turkish continental shelf, the intensity of the observed mean flow has a considerable degree of variability. The relatively strong currents along the straight portion of the coast is reduced significantly in the nearshore region upon encountering irregularities in the form of bays and headlands. As a possible explanation of such blockage by coastal irregularities, a linear, homogeneous wind-stress free model is presented incorporating the constraints of topographic steering and linear bottom friction. Solutions are given for an idealized case of an abrupt indentation on a straight coast adjoining a linearly deepening shelf. The directions preference of blocking and the applicability of boundary layer approximations am discussed. Numerical solutions are obtained for the realistic bathymetry and coastal configuration along the southern Turkish continental shelf. The concepts developed are applied to the observed blocking features.
Abstract
Sea surface height (SSH) variability is presented over the Black Sea during 1993–2005. The 1/4° × 1/4° resolution daily SSH fields are formed using optimal interpolation of available altimeter data. SSH variability reveals distinct maxima in the eastern and western basins, reflecting variations in the corresponding gyres. A joint examination of SSH and sea surface temperature (SST) indicates strong relationship between the two only in winter, with correlations as high as 0.6 or more. This would reflect a steric change in sea surface height due to thermal expansion averaged over a relatively deep winter mixed layer. Newly developed SSH fields also demonstrate a switch to the positive mode of SSH starting from the end of 1996 lasting ≈4 yr. Such a climatic shift is found to be strongly related to large-scale teleconnection patterns. Finally, the daily SSH and SST anomaly fields presented in this paper can supplement various applications in the Black Sea, such as examination of biological production and mesoscale eddy dynamics.
Abstract
Sea surface height (SSH) variability is presented over the Black Sea during 1993–2005. The 1/4° × 1/4° resolution daily SSH fields are formed using optimal interpolation of available altimeter data. SSH variability reveals distinct maxima in the eastern and western basins, reflecting variations in the corresponding gyres. A joint examination of SSH and sea surface temperature (SST) indicates strong relationship between the two only in winter, with correlations as high as 0.6 or more. This would reflect a steric change in sea surface height due to thermal expansion averaged over a relatively deep winter mixed layer. Newly developed SSH fields also demonstrate a switch to the positive mode of SSH starting from the end of 1996 lasting ≈4 yr. Such a climatic shift is found to be strongly related to large-scale teleconnection patterns. Finally, the daily SSH and SST anomaly fields presented in this paper can supplement various applications in the Black Sea, such as examination of biological production and mesoscale eddy dynamics.
Abstract
Recent hydrographic observations obtained in the Bosphorus Strait illustrate several features of the flow that may be related with the internal hydraulics. A two-layer numerical model indicates that the two-way exchange flow may indeed be subject to a series of internal hydraulic adjustments along the strait due to morphological features such as sills, a contraction and abrupt expansion of the width of the strait. The model identifies three distinct regions of the supercritical flow. The lower-layer flow of the Marmara Sea origin is directed to the north towards the Black Sea in a progressively thinning layer and is controlled by the sill located near the Black Sea entrance of the strait. The upper-layer water of the Black Sea origin flows in the opposite direction and is controlled upon reaching the constricted region located about 10–12 km away from the Marmara end of the strait. The upper-layer flow is then matched to the subsequent subcritical conditions by undergoing an internal hydraulic jump and becomes subject to another critical transition near the abruptly widening exit section into the Marmara Sea. The controls exerted by the northern sil and the contraction are connected by a subcritical region whereas the supercritical conditions downstream of these controls isolate the two way exchange from the conditions in the adjacent regions. In this way, the requirement for the maximal exchange is met implying that the Bosphorus Strait achieves the maximum possible transports in the layers depending on the magnitude of net barotropic transport.
Abstract
Recent hydrographic observations obtained in the Bosphorus Strait illustrate several features of the flow that may be related with the internal hydraulics. A two-layer numerical model indicates that the two-way exchange flow may indeed be subject to a series of internal hydraulic adjustments along the strait due to morphological features such as sills, a contraction and abrupt expansion of the width of the strait. The model identifies three distinct regions of the supercritical flow. The lower-layer flow of the Marmara Sea origin is directed to the north towards the Black Sea in a progressively thinning layer and is controlled by the sill located near the Black Sea entrance of the strait. The upper-layer water of the Black Sea origin flows in the opposite direction and is controlled upon reaching the constricted region located about 10–12 km away from the Marmara end of the strait. The upper-layer flow is then matched to the subsequent subcritical conditions by undergoing an internal hydraulic jump and becomes subject to another critical transition near the abruptly widening exit section into the Marmara Sea. The controls exerted by the northern sil and the contraction are connected by a subcritical region whereas the supercritical conditions downstream of these controls isolate the two way exchange from the conditions in the adjacent regions. In this way, the requirement for the maximal exchange is met implying that the Bosphorus Strait achieves the maximum possible transports in the layers depending on the magnitude of net barotropic transport.
